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[clang][Driver][SYCL] Disable SYCL header search paths under -nostd[lib]inc #20583

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Merged
merged 1 commit into from
Nov 13, 2025
Merged

[clang][Driver][SYCL] Disable SYCL header search paths under -nostd[lib]inc #20583

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39 changes: 21 additions & 18 deletions clang/lib/Driver/ToolChains/Clang.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5045,24 +5045,27 @@ void Clang::ConstructHostCompilerJob(Compilation &C, const JobAction &JA,
if (IsMSVCHostCompiler)
HostCompileArgs.push_back("/external:W0");

// Add default header search directories.
SmallString<128> BaseDir(C.getDriver().Dir);
llvm::sys::path::append(BaseDir, "..", "include");
SmallString<128> SYCLDir(BaseDir);
llvm::sys::path::append(SYCLDir, "sycl");
// This is used to provide our wrappers around STL headers that provide
// additional functions/template specializations when the user includes those
// STL headers in their programs (e.g., <complex>).
SmallString<128> STLWrappersDir(SYCLDir);
llvm::sys::path::append(STLWrappersDir, "stl_wrappers");
// Add the SYCL specific header directories as system directories for non
// MSVC compilers.
HostCompileArgs.push_back(IsMSVCHostCompiler ? "/external:I" : "-isystem");
HostCompileArgs.push_back(TCArgs.MakeArgString(SYCLDir));
HostCompileArgs.push_back(IsMSVCHostCompiler ? "/external:I" : "-isystem");
HostCompileArgs.push_back(TCArgs.MakeArgString(STLWrappersDir));
HostCompileArgs.push_back(IsMSVCHostCompiler ? "/external:I" : "-isystem");
HostCompileArgs.push_back(TCArgs.MakeArgString(BaseDir));
namespace options = clang::driver::options;
if (!TCArgs.hasArg(options::OPT_nostdlibinc, options::OPT_nostdinc)) {
// Add default header search directories.
SmallString<128> BaseDir(C.getDriver().Dir);
llvm::sys::path::append(BaseDir, "..", "include");
SmallString<128> SYCLDir(BaseDir);
llvm::sys::path::append(SYCLDir, "sycl");
// This is used to provide our wrappers around STL headers that provide
// additional functions/template specializations when the user includes
// those STL headers in their programs (e.g., <complex>).
SmallString<128> STLWrappersDir(SYCLDir);
llvm::sys::path::append(STLWrappersDir, "stl_wrappers");
// Add the SYCL specific header directories as system directories for non
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@srividya-sundaram srividya-sundaram Nov 11, 2025

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I understand that you have retained the comments from the original code, but could you add some context on why SYCL specific header directories are added as system directories for non MSVC compilers?

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@aelovikov-intel aelovikov-intel Nov 12, 2025

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That should go into a separate PR, possibly merging the implementation of host/device toolchains.

// MSVC compilers.
HostCompileArgs.push_back(IsMSVCHostCompiler ? "/external:I" : "-isystem");
HostCompileArgs.push_back(TCArgs.MakeArgString(SYCLDir));
HostCompileArgs.push_back(IsMSVCHostCompiler ? "/external:I" : "-isystem");
HostCompileArgs.push_back(TCArgs.MakeArgString(STLWrappersDir));
HostCompileArgs.push_back(IsMSVCHostCompiler ? "/external:I" : "-isystem");
HostCompileArgs.push_back(TCArgs.MakeArgString(BaseDir));
}

if (!OutputAdded) {
// Add output file to the command line. This is assumed to be prefaced
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4 changes: 3 additions & 1 deletion clang/lib/Driver/ToolChains/SYCL.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -123,8 +123,10 @@ void SYCLInstallationDetector::getSYCLDeviceLibPath(

void SYCLInstallationDetector::addSYCLIncludeArgs(
const ArgList &DriverArgs, ArgStringList &CC1Args) const {
if (DriverArgs.hasArg(clang::driver::options::OPT_nobuiltininc))
namespace options = clang::driver::options;
if (DriverArgs.hasArg(options::OPT_nostdlibinc, options::OPT_nostdinc)) {
return;
}
// Add the SYCL header search locations in the specified order.
// ../include/sycl/stl_wrappers
// ../include
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9 changes: 9 additions & 0 deletions clang/test/Driver/sycl-nostdinc.cpp
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@@ -0,0 +1,9 @@
// RUN: %clangxx -fsycl -fsycl-device-only -nostdlibinc -fsyntax-only %s
// RUN: %clangxx -fsycl -fsycl-device-only -nostdinc -fsyntax-only %s

// RUN: %clangxx -fsycl -nostdlibinc -fsyntax-only %s
// RUN: %clangxx -fsycl -nostdinc -fsyntax-only %s

#if __has_include(<sycl/sycl.hpp>)
#error "expected to *not* be able to find SYCL headers"
#endif
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